A massive whale that washed up on the north coast earlier this month is thought to have died of natural causes.

Tests on the 43ft leviathan confirmed it as a fin whale, the second largest mammal on Earth after the blue whale.

But experts were unable to pinpoint the exact cause of the animal's death.

The female, which vets from the Agri-Food and Biosciences Institute (AFBI) believe was a juvenile just past its weaning stage, died some time before it ended up beached on Portstewart Strand on October 4.

A statement from the AFBI yesterday confirmed the whale's remains were in a decomposed state when discovered.

"The carcass was in a very poor condition and it had been dead for some time before it came ashore," the statement said.

"The skin was peeling and it had a thin blubber layer. The muscle mass along the back was low and the animal's stomach was empty.

"The body condition of the mammal was considered sub-optimal and natural causes are suspected. However, the exact cause of death is inconclusive."

An operation to remove the beast's huge body quickly got under way, involving the Department of the Environment, the Coastguard and the National Trust.

The team, using diggers, transported the carcass off the sands, transporting it to nearby Craigahulliar landfill site for disposal.

The carcass was initially swept onto rocks below Dominican College in Portstewart one day before it washed up on the strand.

And though it floated back out to sea, it washed in again at the Barmouth further along the coast, to be discovered on Monday morning. The team's removal of the whale's remains to the landfill site avoided the problems faced in 1992 when a 31ft minke whale live-stranded and died on the beach.

At the time a rescue team was overwhelmed by sightseers, with children climbing on the back of the beast and two trophy-hunters cutting off its tail.

Joe Breen of the DoE said the summer of 2015 had been "extraordinary" for sightings of both whales and dolphins off the north coast.

"We followed about 70 or 80 dolphins up and down the coast this summer," he said earlier this month.

"We had reports of humpback whales off Rathlin, and there was an unusual sighting of a Beluga whale off Dunseverick.